1. Field of the Invention
The present invention relates to an aligning device for a disk recording medium such as a Mini Disc (MD), CD, or DVD, and to an information recording/reproducing apparatus in which this type of aligning device is mounted.
2. Related Background Art
Alignment of an optical disk and a rotation shaft of an information recording/reproducing apparatus is conventionally performed by using an aligning member that is provided to a spindle motor that rotationally drives the optical disk. FIG. 10 shows a specific spindle motor that is mounted in a disk drive such as a recordable MD. It should be noted that the disk aligning structure shown in FIG. 10 is disclosed, for example, in Japanese Patent Application Laid-open No. 2003-036585, which was proposed by the applicants of the present invention.
A spindle motor 30 includes a rotor portion 32 that is rotatably supported with respect to a stator portion 31 that is fixedly disposed. The stator portion 31 comprises a stator substrate 33; a housing 34 that is attached to the stator substrate 33; coils 35 that is fixedly disposed surrounding the housing 34 from an outer circumference of the housing 34; and a sliding bearing 36 that is press-inserted and held within the housing 34.
On the other hand, the rotor portion 32 comprises a rotation shaft 37 that is rotatably supported by the sliding bearing 36; a turntable 38 that is attached to the rotation shaft 37; a cylindrical rotor yoke 39 that is attached to the turntable 38 and surrounds the coils 35 from an outer circumference of the coils 35, with a lower end of the cylindrical rotor yoke 39 not connected; a rotor magnet 40 that is provided on an inner side of the rotor yoke 39; an attraction magnet 41 that is provided to an upper surface of the turntable 38; an adjusting member 42 that fits into a turntable cylindrical portion 38a; a regulating member 43 that regulates an upward range of movement for the adjusting member 42; and an urging member 44 that urges the adjusting member 42 upward with respect to the turntable 38.
In addition, a disk 45 is set onto the turntable 38. A fixing disk 46 is mounted from above the disk 45, and a magnetic attraction force of the attraction magnet 41 of the rotor portion 32 pulls the fixing disk 46. The disk 45 is thus mounted onto the turntable 38. A center hole lower edge 45a of the disk 45 contacts with a tapered surface 42a of the aligning member 42 at this point. The aligning member 42 is pressed down in a downward direction against a force of the urging member 44, and the disk 45 is mounted onto the turntable 38 while aligned substantially coaxially with the rotation shaft 37. It should be noted that the urging member 44 is provided in order to respond to tolerance fluctuation of the center hole diameter of the disk 45.
Problems develop if the aligning member 42 is fixed. Fluctuation of the center hole diameter of the disk 45 cannot be tracked. The disk 45 cannot be mounted to the turntable 38 for cases where the center hole diameter is a minimum, and the disk is not aligned when lash with respect to the aligning member 42 becomes large for cases in which the center hole diameter is a maximum. It should be noted that a compression coil spring having a circular cross section is employed for the urging member 44 in the conventional example in order to prevent collapse of the coil when compressed.
The conventional spindle motor 30 is thus configured. A magnetic field that develops in the coils 35 due to suitable electrification of the coils 35 acts in concert with a magnetic field due to the rotor magnet 40 and the rotor yoke 39 of the rotor portion 32. The rotor portion 32 is thus rotationally driven. It thus becomes possible for the disk 45 mounted on the turntable 38 to rotate in synchronism with the rotation of the rotor portion 32 without sliding owing to the attractive force of the attraction magnet 41.
Further, for cases where information is recorded onto or reproduced from the disk 45, it is necessary to accurately align tract positions of the disk 45 with pickup positions that record and reproduce information. In particular, the track positions vary in a radial direction of the disk according to the amount of eccentricity within one disk rotation for cases where eccentricity occurs with the disk 45. For example, a 1.6 μm pitch bit signal is accurately traced and detected for CD reproduction. Positioning is conventionally performed in the radial direction of the disk by using a tracking servo, for example, in order to accurately adjust the pickup positions.
The narrowing of track pitch accompanying higher information density, and the increase in disk rotational velocity accompanying higher transfer rates have been advancing in recent disk recording/reproducing apparatuses. Accordingly, the positioning accuracy of the tracking servo described above demands higher precision and higher speed. However, it is obvious that control at higher precision and higher speed is difficult with the current conventional tracking servo operating range. The operating range of the tracking servo is also tending to become smaller, and therefore it has to be accomplished to reduce the amount of eccentricity.
With publicly disclosed apparatuses, the tolerance fluctuation of the center hole of the disk is made negligible, and high precision alignment is performed, by using a configuration as described above. That is, it is possible for an aligning member that fits into a guide portion of a turntable on which a disk is mounted, the aligning member having a tapered surface contacting with a center hole of the-disk, to slide in a rotation shaft direction of the turntable. However, it is necessary to have a 5 to 20 μm pp sliding gap for a sliding portion because of ambient temperatures, differences in material properties, finishing accuracy, and the like. Accordingly, there is a problem in that the angle of the tapered surfaces changes because the aligning member inclines due to the sliding gap, and eccentricity develops during disk mounting.
In addition, when considering hole fitting of the sliding portion and the guide portion shapes, it is necessary to impart a tolerance fluctuation on the order of 5 to 10 μm to each of the diameter dimensions due to fabrication problems. Accordingly, even with identical designs, the sliding gap described above will have a lash range between the maximum value and the minimum value due to the tolerances of the sliding portion and the guide portion. For example, the sliding gap becomes from 5 to 20 μm when the tolerance of the guide portion is from −10 to 0 μm, and the tolerance of the sliding portion is from +5 to +10 μm.
Further, with these high precision dimensional tolerances, not only is there fluctuation between each component, but the dimensions also change, for example, within the tolerance fluctuation described above for the sliding portion of one individual component. Accordingly, the eccentricity that develops from the incline of the aligning member changes greatly because there is a range in the sliding gap. However, in order to maintain a constant sliding gap, work for further reducing the tolerance fluctuation of the components, selecting each component by inspecting its dimensions, and the like becomes necessary, and there is a problem in that this work leads to higher costs.